Heli-coil sparkplug thread. Steel vs Aluminum

[mattcfish]

After cleaning up my heads for dual plugging I just noticed that one of the heads I've been using for the last 21 years has a Heli-coiled spark plug hole. A magnet doesn't stick to it, so it must be Stainless. I've read about how steel inserts change the heat range of your spark plugs (and can even act as a glow plug) and that aluminum threads are prefered for aluminum heads. I haven't really noticed a problem, but I'm increasing compression and will be using a 336 cam so things might change.
It looks like there's only two options for aluminum inserts. Timesert http://www.timesert.com/html/bigsert_sparkplug.html
and Locknstitch http://www.locknstitch.com/sparkpluginserts.htm. The Locknstitch seems like a superior product because it's designed to prevent cracking, but one kit costs more than a completely rebuilt head.
The Timesert version is cheaper, but cracking could be an issue.
Anybody have experience with either one? Should I even worry about re-doing the threads?

[Major Softie]

Should I even worry about re-doing the threads?

I wouldn't. If the current insert is working fine, I'd live with it. If you want to be anal about it, but a little less anal than you're considering, Heli-coil the other head so that at least they will be identical.

[George Ryals]

I have steel Timeserts in my dual plugged '74 Harley Super Glide (aluminum heads) on the right side and steel Heli-coils in the left side. No problems for 7 years.
I'd leave the Heli-coil alone.

[mattcfish]

I'm surprised there isn't more debate on this subject. There's a lot of banter on the Hot Rod cage driver sights. I'd hate to have to cut up the good threads on my other head to install a matching Stainless Heli-coil. I'm moving compression up from 9:1 to close to 10:1. Is the unbalanced heat transfer on the plugs really a non-issue on airheads? Maybe with the dual plugging it really is less of an issue.

[George Ryals]

You can always get the one head welded up and redrilled and tapped into the aluminum, eliminating the helicoil.

Technically there is a difference in heat transfer with a helicoil just because there is the extra interface that the heat has to pass through. I seriously doubt that anyone has ever actually measured the difference. I can't believe it would make a heat range difference.